Intensity modulated radiation therapy (IMRT) has been used for organ-preserving whole breast irradiation. IMRT also has been found to improve the ability to conform the treatment volume to concave tumor shapes, for example when the tumor is wrapped around a vulnerable structure such as the spinal cord or a major organ or blood vessel. In IMRT, computer-controlled accelerators distribute precise radiation doses to specified areas. The pattern of radiation delivery is determined using tailored computing applications to perform optimization and treatment simulation (commonly referred to as treatment planning). The radiation dose applied to the patient is controlled by controlling, or modulating, the radiation beam's intensity. In a typical treatment plan, the radiation dose intensity is elevated near the gross tumor volume while radiation among the neighboring normal tissue is decreased or avoided completely, in order to maximize dose to the target tissue (typically the tumor) while minimizing dose to non-target tissues.
In some examples, IMRT has been shown to improve target dose homogeneity (1, 2) and reduce acute skin toxicity (3, 4) over conventional breast radiation therapy approaches that rely on wedged compensators for beam modulation. In some examples, the dose distributions produced with IMRT have also translated into better clinical results versus conventional methods, as shown in two randomized trials (4, 5). The use of IMRT in breast radiation therapy and how one defines IMRT in the context of breast treatment has been debated (6, 7). As well, greater amounts of resources and expertise are often required to implement and maintain a breast IMRT planning approach (7).
An example of automated planning for breast tangents has previously been implemented for three-dimensional conformal breast tangents treatment plans (8). That algorithm was developed to optimize beam energy, beam weighting, wedge angle and wedge orientation, to produce treatment plans. In that example, the automated process was found to reduce the planning time and to result in more reproducible plans as compared to the conventional clinical manually-designed plans. However, that example was not related to IMRT. Further, in that example, not all of the planning was automated, for example determination of parameters such as gantry angle and collimator angle was not automated, nor regions of interest segmentation nor incorporation of the cavity into the optimization.
Automation for IMRT may involve optimization parameters, such as the number of segments and minimum area of segments allowed for generating the modulated field, that do not need to be considered in conformal treatment plans. Such IMRT parameters should be considered to help ensure that generated treatment plans are able to provide sufficient modulation without making the segments too complicated, for example.
It would be desirable to provide a method and system for treatment planning of radiation therapy that avoids or reduces the need for extensive user interaction and iterative trial-and-error to generate treatment plans